Schaefer's Blocks rely on a variety of sheaves designs and scorings. Schaefer sheaves are design to be compatible with Schaefer products. There is a risk of incompatibility or failure when using Schaefer sheaves in blocks manufactued by anyone other than Schaefer Marine.

Aluminum UC Sheave with Torlon Ball Bearings, these extremely low friction ball bearing sheaves accommodate both line and wire. High strength self-contained Delrin™ bearing package, and Nomex™/Teflon™ self-lubricated bushing is used in all "UC" sheaves . The combined benefits of the design mean easier turning under the heaviest loads.